Telephone answering machines for automatically answering a telephone, generating a prerecorded greeting message (i.e., outgoing announcement or OGA), and recording an incoming message are commonly available. Such an answering machine is known from the GE model no. 9882, manufactured by Thomson Consumer Electronics, Inc. Indianapolis, Ind. This answering machine is capable of answering telephone calls received via the "tip" and "ring" terminals, as is standard practice.
Telephone companies have been installing four-line cables to homes for quite some time. Two of the lines are the above-noted tip and ring lines and occupy the center terminals of the standard 4-pin modular plug. The other two lines are referred to as A and A1 respectively, and occupy the outer terminals of the standard 4-pin modular plug. Previously, the A and A1 lines were unused. However, telephone companies recently have begun using lines A and A1 to connect a second telephone line (i.e., central office or CO line) to private homes. Unfortunately, this new use for the A and A1 lines has created an incompatibility problem with respect to telephone answering machines, in that the A and A1 lines are also used in commercial offices for illuminating "line-in-use" lamps on business multiline telephones (i.e., keysystem units). That is, an answering machine designed for use with keysystem-compatible equipment will answer a telephone call on the tip and ring terminal pair, and place a low impedance across the A and A1 terminal pair to indicate that the line is in use. If such a keysystem-compatible answering machine is used at home, then the second telephone line (i.e., the one connected via the A and A1 lines) will be disabled by the automatically-connected low impedance, when the first telephone line is answered. If a non-keysystem-compatible answering machine is used in the office environment, then the telephone call will be answered, but undesirably, the line-in-use indication will not be provided.
A further problem exists in the home environment, in that a user may want to have his answering machine answer his second telephone line. A home answering machine which can answer either of two telephone lines is known from the Panasonic model KX-T2740. However, this model has two modular input jacks, and requires two separate telephone lines to be connected (i.e., it cannot not answer telephone calls connected via terminals A and A1 of the telephone cable without the use of an additional adapter to split the telephone lines onto separate cables). Known keysystem-compatible answering machines have no capability for answering telephone calls on the A and A1 lines.